Compact Undulator for Cornell High Energy Synchrotron Source

Motivated by the needs of Cornell High Energy Synchrotron Source (CHESS), we developed and are now constructing a novel type of planar undulator magnet called CHESS Compact Undulator. The device consists of two pure permanent magnet (PPM) arrays mounted inside of a rectangular box-like frame on linear bearings providing magnet array motion along the beam axis. The outside frame dimensions are 156 mm 148 mm. Undulator is 1 meter long. It has 5 mm constant gap. The magnetic field strength is controlled by the array longitudinal motion (adjustable phase scheme). Magnetic structure has 24.4 mm period and maximum peak field 1.1 Tesla. The PM material is Nd-Fe-B of 40UH grade. The undulator magnet will be enclosed in a 273 (10.75") mm diameter cylindrical vacuum vessel while the driver mechanism responsible for moving the magnet array will be placed outside. The following sections describe mechanical and magnetic design of undulator and present results of the magnetic field measurement and evaluation of vacuum properties.